Processes have been disclosed for the chlorination of hydrocarbons using hydrogen chloride as the source of chlorine in U.S. Pat. Nos. 4,899,000; 4,990,696; 5,097,083; 5.099,084; and 5,185,479. These processes have several features in common. They all rely on the oxychlorination of perchloroethylene with hydrogen chloride and oxygen to produce hexachloroethane. In a separate reaction zone, the hexachloroethane so produced is reacted with a hydrocarbon to yield a chlorinated hydrocarbon, hydrogen chloride and perchloroethylene. By recycling the hydrogen chloride and perchloroethylene produced in the second step to the oxychlorination reaction, a continuous process can be achieved.
The advantages of these processes over the prior art are significant. By conducting the chemical reactions in two segregated zones, the hydrocarbon feed is chlorinated in the absence of oxygen or air. Thus, combustion is avoided and the production of unwanted byproducts minimized. Furthermore, these processes rely on the use of conventional equipment, the characteristics of which are well known.
Notwithstanding the advantages of these existing processes, certain drawbacks are apparent. Hexachloroethane sublimes at about 187.degree. C., which requires that it must be heated above this temperature to transport it, or a solvent such as perchloroethylene is needed. Furthermore, even though the hexachloroethane is sealed within the system, its relative toxicity is a potential hazard.
Finally, the equilibrium between the dehalogenation of hexachloroethane and its regeneration from perchloroethylene may constrain the operating conditions of the process. The oxychlorination reaction temperature must be maintained sufficiently low in order to favor the formation of hexachloroethane. At higher temperatures, the hexachloroethane will decompose to perchloroethylene and chlorine.
Therefore it is an object of the present invention to provide a new chlorinating agent or family of compounds that do not possess the disadvantages of hexachloroethane. These compounds can function as chlorine carriers enabling the transfer of chlorine from one reaction zone to another. These compounds must be convenient to handle and be effective in the process. They cannot sacrifice any of the positive features of hexachloroethane.
These and other objects, features, and advantages of the invention will be apparent from the following description and the accompanying drawing.